Inflation at Askja, Iceland. New and revisited relative microgravity data.

<p><span>In August 2021 Askja caldera in Iceland </span><span>started to </span><span>show uplift after decades of subsidence. </span><span>Th</span><span>e</span><span> uplift signal is centered at the northwest</span><span>ern</span><span> edge of lake </span><span>&#1254;</span><span>skjuvatn </span><span>and an order of magnitude larger than the subsidence in the last decade</span><span>. </span><span>In </span><span>September</span><span> 2021</span><span> a geodesy campaign was carried out at Askja, including </span><span>relative </span><span>microgravity measurements </span><span>acquired with the use of </span><span>tw</span><span>o</span><span> Scintrex CG-5 instruments. </span><span>Relative m</span><span>icrog</span><span>r</span><span>avity </span><span>campaigns</span><span> at Askja are not straightforward due to the long walking distances between sites, which makes a &#8220;double loop&#8221; procedure impossible. </span><span>We revisit existing Scintrex </span><span>relative </span><span>microgravity data sets</span> <span>(</span><span>2015 </span><span>onward)</span><span> and analyse data using the same </span><span>joint</span> <span>weighted least squares inversion routine</span><span>. We </span><span>define</span><span> recommendations for future </span><span>relative </span><span>microgravity campaigns at Askja </span><span>which will be</span> <span>i</span><span>mportant to establish the cause of the ongoing uplift. </span><span>T</span><span>he density of subsurface magma is only identifiable with microgravity data. </span><span>Knowledge of t</span><span>he type of magma </span><span>accumulating under Askja</span> <span>is vital to assess</span> <span>possible </span><span>hazard impl</span><span>i</span><span>cations.</span></p>